I need help Identifying a couple wires.

So just a quick update; Today I put in a couple hours on the Dart, I added an aftermarket 6-gang fuse block to the mix so that i can add my future circuits to MY wiring, not the cars 46y.o. circuits :)

I chose to take power for the block right off the main stud for the starter relay, since it's now the main bus for the dash. I also ran an 8ga wire from the alternator to accommodate a larger output unit in the near future.

Next, I replaced the inner tail lamp sockets. The originals were fine, but the 1156 bulb that was in them is as bright as the outer's are with the brakes applied. I view this as a safety hazard. It is my understanding that the correct bulb is a pain in the *** to locate, so i simply chose to go to an 1157 socket, but only powered the dim side of the lamp. The other wire is unhooked. So now i can run the far more common 1157 on the inner and outer without the brightness issue.

Now comes the interesting part..... I get in the car to do a light check......nothing. No power, no start, not a word from the car. So I grab my trustee fluke 88 and dig in. 12.2v at the battery, relay, and even to the bulkhead. So I jump the relay with a screwdriver, nothing! Im like WTH??? Ground problem? but how? everything I did was on the power side?

So I run to AutoZone and pick up a new starter relay after ohming out my ground strap and finding nothing, and that took care of the issue. Easy enough, but strange nontheless.

Thinking that this ground issue may have onset slowly as most ground issues do, I wondered if my alternator output had risen. Low and behold it has, idle output is up from 9-9.5A to 12-12.6A. The stud for the Relay was clean, which is to say I wire brushed it a couple weeks ago doing all the work mentioned above. My question is, how did this ground affect my output??

I even unhooked the 8ga wire to rule out the wire size difference, which I seriously doubted was the issue anyway, but just to be sure. Wire size was not the x factor, that ground had to be